Ball valves typically include a valve body that includes a plurality of ports typically ranging between two ports and four ports. A valve member within the valve body, depending on its orientation within the valve body, selectively directs fluid between selected ones of the various ports or may entirely stop fluid flow through the valve body. As such, ball valves include seals interposed between the various ports and the valve member to prevent fluid from bypassing the valve member, i.e. leaking around the valve member and circumventing the desired fluid flow configuration.
Unfortunately, due to machining tolerances of the valve member and valve body, it has been difficult to ideally place and size fixed position seals for perfect, leak-free, seal-off. Further, merely using a seal that is oversized and compressing it within the valve body to compensate for the variations in tolerances can impart large loads on the valve member that make it more difficult to rotate the valve member. These large loads can require larger, more powerful actuators to position the valve member, leading to more costly actuators and more costly operation.
Compounding the problem of using fixed position seals is the fact that the pressure differential across a given port can vary depending on the flow direction of the fluid through the port or valve member. The changes in pressure can cause the walls of the valve member to flex or cause the valve member to move within the valve body. Fluid flow in one direction may move the seal and valve member out of sealing contact, while fluid flow in another direction may move the seal and valve member into sealing contact. As such, depending on the fluid flow and pressure differential, a fixed position seal may or may not provide adequate leak-free sealing between the valve member and valve body.
There exists, therefore, a need in the art for an improved ball valve and sealing configuration that overcomes these and other problems existing in the art. The apparatus and method of the present invention provides such a ball valve and dynamic sealing configuration.